1. Field.
This invention relates to concrete curb forming and extruding apparatus. More particularly, it relates to a concrete curb forming and extruding apparatus with wheel adjustment locks, and a slip form shaping the cementitious material into a continuous curb forced therethrough by an extruder which receives materials stored in a hopper. The extruder has a reciprocating elliptical orbit compacting member which on the compaction stroke simultaneously moves forward to compact the concrete and lifts upward slightly just before the return stroke to force the compressed concrete against the upper surface of the slip form to fill the same and form the continuous curb. On the return stroke, it moves back and slightly downward to collect more concrete from the hopper for compaction on the compaction stroke. This elliptical or arcing orbital movement of the compaction end of the compaction member will hereinafter be referred to as an elliptical orbit or elliptical orbit compaction.
2. State of the Art.
Present concrete curb forming and extruding machines have a reciprocating ram or an auger to force concrete material into a slip form forming a running curb. The concrete material is usually of a dry consistency to hold the form of the curb after being extruded from the machine. The dry consistency of the material causes it to bridge from side to side in the hopper and not fall through into the compaction chamber. It is common practice to have two men run the machine--one to steer and control the machine while the other shovels small amounts of material into and through the hopper.
The ram type of curb forming and extruding machines move ahead when a shovel of material is put through the hopper. This forward movement is generally two or three inches per stroke. The ram then cycles without moving the machine until the next shovel of material is put through the hopper. This erratic action causes voids which have to be filled. It also causes curb cracks when the machine coasts at the end of the stroke.
These ram type machines use a gear box to reduce the speed with a crank arm connected to a flat faced member which is pushed by the crank through the compaction chamber or housing displacing the curbing material through the slip form to form the curb. May, U.S. Pat. No. 4,566,823 is an example of a manually operable curb extrusion device with interchangeable molds and compacting members wherein building material is placed in a receiving hopper and falls into a compacting chamber where a power driven and reciprocating compacting member compacts the material into the extrusion mold where it is shaped and extruded. The curb extrusion device is manually directed or steered along the desired course via an adjustable steering mechanism, and has a hopper with one straight upright side, screw-on molds, and adjustable legs connected to the wheels. Eggleton, U.S. Pat. No. 4,310,293 is another example of a ram driven concrete curb molding apparatus.
Ram machines have been the most popular because of their positive upward travel. However, straight compressive forces are not conducive to better compaction. Varying sizes of particles resist compaction and stack one against another, leaving voids or cavities between the particles. Voids cause porous concrete with diminished compressive test strengths.
The ram of the ram curb forming machine also picks up some of the concrete material on the return back-stroke which is then deposited as a trail of material down the sides of the curb as waste. This slag has to be cleaned up or pressed down out of sight and buried. Ram machines, as the speed of the ram is increased, tend to jump ahead and then coast forward at the end of the stroke which puts cracks in the top surface of the curb. Loose parts on the machine, such as wheels, can also leave marks in the extruded curb.
Auger type curb forming machines use an auger to move material through a compaction chamber into the slip form,. McKinnon, U.S. Pat. No. 5,354,189, unlike other auger systems, will travel as effectively up and down hills as it employs vibrating augers which apply pressure for compaction to forces material through a mold rearward, thereby propelling the machine forward. In addition, the vibrating augers prevent material from becoming captive to turn with the augers. Other auger systems are: Smith, U.S. Pat. No. 3,137,220 which discloses a curb-laying machine with a number of oppositely rotating augurs to extrude the concrete for forming curbs; Parrish et al., U.S. Pat. No. 5,018,955 utilizes a single auger to extrude the concrete and features a slip-on curb form with various adjustment options; Bunn, U.S. Pat. No. 4,548,565, Coho. Jr. et al., U.S. Pat. No. 3,915,584; and W. E. Canfield et al., U.S. Pat. No. 2,818,790.
Cited for general interest are: Aparicio, U.S. Pat. No. 3,915,583 disclosing a paving machine slip form, Baucum, U.S. Pat. No. 4,298,293 disclosing a drag line operated slip form curb forming machine, and Leone, U.S. Pat. No. 4,984,932 disclosing an apparatus for continuous formation of concrete curbs via the raising and lowering of the molding to form thresholds for driveways, and intermediate tapering sections for transitions between full height curbs and thresholds.
The present invention avoids the ram compaction waste problems, and provides an improved curb forming and extruding machine which provides a curb having strong compressive strength with a smooth finished look requiring no manual troweling. The elliptical orbit compaction also allows a shovel full of material to be fed more evenly through the apparatus over a number of ram strokes. This builds a more evenly compacted continuous curb without voids or cracks.